Vista - Problems Reading Shared File (The local device name is already in

I have a very odd problem with my shared network files. I run a desktop with
Windows 2000 (don't ask!) and a laptop with Vista Home Premium. The desktop
is plugged into the wireless router but the laptop uses wireless.

After a lot of trial and error I have got the internet working on both and
have set up both pcs to share files from My Documents (and Documents on
vista). This seems to be working mostly as I can read the laptop files from
the desktop and the laptop recognises the shared desktop files.

However, when I try to access the desktop drive from the laptop (even right
clicking) it goes into a spin and eventually comes back with the message "The
local device name is already in use" . I have tried changing the drive
letters and altering the network name of the desktop drive but everything
results in the same error message.

This sounds like I have done the hard bit but it is just not quite there.
It's probably something obvious. Can anyone help?